The present invention constitutes an improvement in the apparatus and method for installing concrete piles according to prior U.S. Pat. Nos. 3,851,484 and 3,851,485, both issued to Steding on Dec. 3, 1974.
A problem can arise during the installation of concrete piles in accordance with the apparatus and method disclosed in the above patents where soft soil below the water table is encountered and where the rate of penetration of the plow point into the soft soil is not controlled. This problem can result in the formation of imperfect concrete piles, and it is the primary object of the invention to alleviate this difficulty in a simple, effective and economical manner.
More particularly, if the pile driving hammer is allowed to strike the pusher with such force that the resulting penetration of the plow point under each hammer blow is in the order of six inches to one foot, then, at the point of impact of the pile hammer with the pusher, the plow point is temporarily driven from beneath the grout column above it, forming a void between the plow point and grout column. Such void cannot exist in actuality because of a nearly perfect vacuum therein, and therefore the void must be instantly filled either with grout from above or with the surrounding soft soil adjacent to the concrete pile being formed. The vacuum tends to pull the surrounding soft soil into the void in some cases, resulting in decreasing the diameter of the pile.
This entire problem is corrected and eliminated by the present invention simply by providing an effective vacuum relief arrangement in the apparatus being employed to form a concrete pile in soft soil below the water table or in other situations where the formation of the described vacuum could result.
Another important object of the invention is to provide a vacuum relief passage means in a concrete pile installing apparatus whose presence does not impede the normal mode of use of the apparatus to form concrete piles in accordance with the teachings of the above-referenced prior patents.
Other features and advantages of the invention will become apparent to those skilled in the art during the course of the following detailed description.